1. Field of the Invention
The invention relates to a heating device with a heating element of a material with positive temperature coefficent, of which two opposite sides are contacted by planar electrodes and give off the heat produced through the electrodes and planar sheets of insulating material covering the same to two heat-absorbing surfaces of a heater.
2. Description of the Prior Art
Such heating devices have been proposed in German Patent Application No. P 27 43 880 (corresponding allowed U.S. application Ser. No. 946,634 now U.S. Pat. No. 4,177,375) and German Petty Patent Application No. G 77 30233. There, the sheets of insulating material are placed on the electrodes and are pressed by a press fit onto the electrodes in the assembled condition in order to achieve good heat transfer to the sheets of insulating material. This design has the disadvantage that in the course of time the press fit becomes loose and the heat transfer is impaired.